Multilayer plastic film with separable layers for covering of inflated greenhouse

ABSTRACT

A multilayered polymeric film for covering an agricultural structure or greenhouse is described herein, wherein the film contains adjacent layers that are capable of delamination from one another. A method of covering an agricultural structure or greenhouse with the multilayered polymeric film can comprise inserting gas between adjacent layers of the film.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.13/452,473, filed Apr. 20, 2012, which claims the benefit of UnitedKingdom Application No. GB1106677.6 filed Apr. 20, 2011. Thisapplication hereby incorporates by reference the U.S. and foreignpriority applications enumerated herein.

FIELD

The present disclosure relates to a multilayered polymeric film or sheethaving layers that are capable of delamination, suitable for use incombination with agricultural structures, such as greenhouses oragricultural tunnels, and for packaging applications. More particularly,the disclosure is directed to a polymeric film comprising at least twoadjacent layers of different polymeric composition, wherein the layersdo not significantly adhere to one another and are thus separablepost-production. The polymeric film or sheet is co-extruded using knownextrusion blown or cast techniques.

BACKGROUND

Greenhouses or other agricultural structures, such as agriculturaltunnels, may be covered with flexible films comprising polymericmaterials that are tailored to provide a favorable environment for thecultivation of crops and plants. The covers are employed to provideprotection for the crops grown underneath from adverse weatherconditions and to create a greenhouse effect by selectively filteringsolar radiations.

The composition of the polymeric film is important and, in particular,should provide the film with: adequate mechanical properties, includingresistance to tears, film elongation and stresses from atmosphericagents; high levels of light transmittance, especially in the region ofchlorophyll photosynthesis; capacity to absorb radiation in the farinfrared region of the spectrum, i.e. from 7000 to 13000 nm; and goodlight stability for an extended lifetime.

To obtain better thermal insulation during the night and reduce energyconsumption, such greenhouses may use several separate films to create alayered structure that is subsequently inflated. For example, thegreenhouses are covered with two, or rarely three, separate films whichare individually installed one above the other and then air is insertedbetween them to keep them apart. This practice is thought to achievebetter thermal insulation and also help in the case of strong winds andsnow, as the air between the layers helps to keep the structure welltensioned and prevents any mechanical fatigue that would result fromuncontrolled movement in the wind. The lifetime of plastic films oninflated greenhouses is also improved compared to single film uninflatedgreenhouses.

The covering for inflated greenhouses is achieved with two or rarelythree films, exhibiting the same or different characteristics. The filmsare laid on the greenhouse structure and fixed with special clips orprofiles, one after the other. In some geographical regions a singletube is laid on the structure and fixed. In both cases, after fixing thefilms or tube, air is inserted to keep the films or the two sides of thetube apart.

In practice, the installation process is not easy because the films mustbe unrolled and unfolded at heights of from 4 to 6 meters from theground and on long lengths, usually from 50 to 100 meters, and thenfixed at the sides of the span throughout their length. Afterwards, thesame process has to be repeated for the second film and so on. If duringthe installation there are winds, there is a danger of the films beingtorn and for the installers to be injured. Due to these reasons and alsodue to the time it takes to install the two (or more) films, the processis rather expensive.

Using tubes also has disadvantages because the upper and lower filmcannot be different, as required by best practices (e.g. a non-thermicmechanically strong upper film and a thermic film with anti-drippingcharacteristics on the lower one), and also because there arelimitations on the width of the span (tubes are typically less than 8meters), because greenhouse film tubes are currently made with acircumference of up to 16 meters at most.

WO97/00006 describes a greenhouse film having variable light diffusionproperties. In one embodiment, the film may be combined with a separate,clear low density polyethylene film to produce a double-skin covercapable of being attached to a greenhouse structure and inflated withair.

Accordingly, there is still a need for an improved polymeric film thatcan be used in association with agricultural structures, such asgreenhouses, agricultural tunnels, animal husbandry buildings, plantexpositions etc. There is also a need for an inflatable film exhibitingexcellent mechanical and optical properties that can be installed in afaster and simpler way, to a variety of shaped greenhouses.

SUMMARY

In accordance with a first aspect of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer connected thereto, wherein layer (i) and layer (ii) arecapable of delamination from one another, the at least one furtherpolymer layer (ii) comprises a polymeric material selected from thegroup consisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, and the film hasa luminous transmittance greater than 30%. Preferably, the delaminationis effected in situ, i.e., when in use with an agricultural structure orgreenhouse.

The difference in chemical composition between said layers identifiedabove, and/or their associated physical properties, means that they donot significantly adhere to one another and thus delaminate easily withthe application of a relatively low amount of force to the layers, suchas the application of fluid (preferably air) pressure, between thelayers.

In accordance with a second aspect of the disclosure, there is provideda multilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer, wherein at least 80% of layer (i) and layer (ii) aredelaminated, the at least one further polymer layer (ii) comprises apolymeric material selected from the group consisting of polyethylene,polypropylene, ethylene vinyl acetate copolymer, ethylene butyl acrylatecopolymer, thermoplastic polyurethane, and combinations of two or morethereof, and the film has a luminous transmittance greater than 30%.Delamination of the film allows a gas, preferably air, to be insertedbetween the separable layers of the polymeric film and creates athermally efficient structure when the film is used in association withan agricultural structure, such as a greenhouse or tunnel.

In accordance with a third aspect of the disclosure, there is providedan agricultural structure or greenhouse, wherein the structure comprisesa polymeric film according to the first or second aspects of thedisclosure. The film in its inflated form creates a thermally insulatinglayer for improved thermal economy and provides a more physically robustnature to the entire structure.

In accordance with a fourth aspect of the disclosure, there is provideda method of covering an agricultural structure or greenhouse with thepolymeric film according to the first aspect of the disclosure,comprising the step of inserting gas between (i) the at least one layercomprising the polyamide and/or ethylene vinyl alcohol and (ii) the atleast one further polymer layer. The process is typically carried out insitu when the film is in combination with the agricultural structure andthus allows the film to be easily transported in a rolled, deflated formfor erection on site.

The inventors have found that the polymeric composition of adjacentlayers is important in providing a film in which specific layers do notsignificantly adhere to one another. They have also found that theselayers may be delaminated by introducing air (at elevated pressure)between the layers that do not significantly adhere to one another andthus provide a single film product capable of being employed as aninflatable film with agricultural structures.

The film of the present disclosure is advantageous because it can beinstalled on a greenhouse or related agricultural structure in a singleprocess, can be fixed in a faster and simpler way and then two or morelayers can be separated by inserting air between them. This reduces therisks involved with the installation process (such as resistance totear) and reduces the costs of production, because only a single film isrequired rather than two or three separate films as is currentlyrequired for inflated greenhouses. The present film also improvesthermal insulation.

Another advantage is the impact on logistics, since instead of using twodifferent types of film, for example one non-thermic for the outer filmand one thermic anti-drip for the inner film as is usually done, onlyone film is used and can be transported much more easily.

DETAILED DESCRIPTION

Disclosed herein is a multilayered polymeric film for use in combinationwith agricultural structures. A large variety of structures areavailable for plant growth purposes including traditional framegreenhouses, geodesic frame greenhouses and tunnel greenhouses. Thepolymeric film described herein is particularly suited to commercialscale greenhouses. The film may be used for a portion or the whole ofthe greenhouse. The term greenhouse is used to mean any form ofagricultural structure exposed to sunlight, within which a cultivationarea is defined for the growth of crops, plants and the like or for thepresentation and sale of ready plants. It is also used to define anymetallic or wooden structure covered by plastic film that can be usedfor a variety of applications, such as a warehouse, as an animalhusbandry building, as a temporary shelter for people etc.

The polymeric film according to the disclosure includes at least twoadjacent layers which are composed of different polymeric materials. Thedifference may be chemical composition or physical attributes,preferably chemical composition. The difference in composition allowsthe layers to be delaminated after the film has been produced, since thelayers do not significantly adhere to one another or become irreversiblybonded as a result of the production process. At least one of theaforementioned layers of the film is comprised of a polyamide and/orethylene vinyl alcohol. In particular embodiments, the layer iscomprised of a polyamide.

The terms “delamination” and “the layers do not significantly adhere”means that the layers preferably retain a unitary structure until asufficient delaminating force is applied. Such a force is preferablyachieved by blowing air (or other fluids) between the layers. Such aforce may also be achieved by at least a part of the film beingdelaminated by hand (for example by rubbing or pulling the layersapart). Such a method is usually used to initiate the delamination,which is completed by the application of air pressure.

In applications having different end uses for the film, specialtie-materials or other adhesive materials have been used when suchpolymer layers are present in order to ensure that sufficient adhesionis achieved. Nevertheless, even if tie-materials are not employed, it isnot known in the art that an inflatable film can be made by delaminatingadjacent layers that do not significantly adhere to one another.

Thus, the present inventors have found that by using (i) at least onepolyamide and/or ethylene vinyl alcohol layer in conjunction with (ii)at least one further polymer layer that does not significantly adhere toit, it is possible to then easily delaminate the layered structure andproduce an inflatable film as a single product with a layer of airbetween the aforementioned layers of the film. It is also within thescope of this disclosure to have additional layers in the film whichcontain tie-materials.

In a further embodiment, there is provided a polymeric film comprisingthree, four, five, six, seven, eight, nine, ten or more layers, in whichtwo or more of the layers are capable of being delaminated, for example3, 4 or 5 of the layers are capable of being delaminated. For example,the film may contain at least three layers in which it is possible todelaminate each layer and provide an inflated product sandwiching atleast two layers of air. A film with two or more layers of air canresult in greater thermal insulation than a film with one layer of air.

In the case of an arrangement in which three layers are delaminated, atleast one of these is comprised of a polyamide and/or ethylene vinylalcohol. Usually such a layer is the middle of the three layers and isenclosed by two other layers comprised of polymers that do notsignificantly adhere to it. However, it is also possible that the twooutside layers are comprised of a polyamide and/or ethylene vinylalcohol and the middle layer is comprised of a polymer that does notsignificantly adhere to it. In both of these cases, it is possible todelaminate the non-bonded layers to provide a film with two layers ofair separating the polymer layers. Thus it is possible to produce atriple layer inflated greenhouse film for even further enhancedinsulation properties. It is also possible to apply this principle toeven higher numbers of layers to produce a film with three or moreinsulating air layers.

The layer (i) comprising the polyamide and/or ethylene vinyl alcoholpreferably contains greater than 20 wt % of said polymer, preferablygreater than 50 wt %, more preferably greater than 60 wt %, even morepreferably greater than 75 wt %, most preferably greater than 90%thereof. Preferably the polyamide is selected from the group consistingof polyamide 6, polyamide 6/6, polyamide 6/66, polyamide 6/610,polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T, polyamide4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide 6/69,polyamide 66/610 polyamide 6/12, polyamide 5/10, polyamide 6I, polyamidenanocomposites and combinations of two or more thereof. Other polyamidesmay also be suitable. Polyamides are beneficial because they do notadhere to other polymeric materials in the production process andbecause they absorb infrared radiation and thus enhance thethereto-insulating properties of the film. Ethylene vinyl alcohol isalso beneficial for these reasons and preferably has 10 to 50% ethylenecontent, more preferably 28 to 48% ethylene content.

The remaining layers of the film are preferably employed to provide thefilm with physical robustness. Thus, in addition to the aforementionedlayer (i) of a polyamide and/or ethylene vinyl alcohol, the polymericfilm according to the disclosure further comprises (ii) at least onefurther polymer layer connected thereto. The composition of this layeris such that it is comprised of a material that does not significantlyadhere to (i) the polyamide and/or ethylene vinyl alcohol layer duringthe production process. Layer (ii) comprises a polymeric materialselected from the group consisting of polyethylene (including lowdensity polyethylene, linear low density polyethylene and metallocenelinear low density polyethylene), polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplastic polyurethaneand combinations of two or more thereof. Other materials suitable forgreenhouse applications may also be applicable. The layer (ii)preferably contains greater than 10 wt % of said polymer or polymers,more preferably greater than 50 wt %, even more preferably greater than75 wt %, most preferably greater than 90% thereof.

In some embodiments, a combination of polymers in layers (i) and (ii)are polyamide and polyethylene, respectively. In other embodiments, acombination of polymers in layers (i) and (ii) are polyamide andethylene vinyl acetate copolymer, respectively. Another combination ofpolymers in layers (i) and (ii) are polyamide and ethylene butylacrylate copolymer, respectively. Another combination of polymers inlayers (i) and (ii) are ethylene vinyl alcohol and polyethylene,respectively. Another combination of polymers in layers (i) and (ii) areethylene vinyl alcohol and ethylene vinyl acetate copolymer,respectively. Another combination of polymers in layers (i) and (ii) areethylene vinyl alcohol and ethylene butyl acrylate copolymer,respectively.

In certain embodiments of the disclosure, layer (i) comprises less than20% of the materials employed in layer (ii), preferably less than 10%,even more preferably layer (i) is substantially free of any materialsemployed in layer (ii). In another embodiment, layer (ii) comprises lessthan 20% of the materials employed in layer (i), preferably less than10%, even more preferably layer (ii) is substantially free of anymaterials employed in layer (i).

The characterising feature of the film according to the presentdisclosure concerns the ability of specific layers to undergodelamination without significantly affecting the structural integrity ofthe individual layers, or there transparency to sunlight. In particular,(i) the at least one layer comprising a polyamide and/or ethylene vinylalcohol and (ii) the at least one further polymer layer are capable ofdelamination from one another. In particular embodiments, the layerscapable of being delaminated may have an average delamination strengthof less than 450 g/15 mm, preferably less than 250 g/15 mm, morepreferably less than 100 g/15 mm, even more preferably less than 75 g/15mm, most preferably less than 30 g/15 mm. In certain embodimentsdisclosed herein, no interface of layer (i) with layer (ii) has adelamination strength of greater than 450 g/15 mm, preferably no morethan 250 g/15 mm, more preferably no more than 100 g/15 mm, even morepreferably no more than 30 g/15 mm. The delamination strength may bedetermined using a peeling tester (Shimadzu's trade name, EZ-TEST)T-peel test (ASTM D1876) at a speed of 100 mm/min on a test piece of 15mm width cut from the laminate film. In certain embodiments, it may bepreferable that at least 75% of the film area, more preferably 90%, hasan average delamination strength as described herein.

The films of the present disclosure may have high luminous transmittancecharacteristics. The films of the present disclosure may have low hazecharacteristics, although this depends on geographical location ashigher levels of haze may be desirable in certain areas of the world.Haze and luminous transmittance of the film of the present disclosurewere measured following the ASTM-D1003-92 Standard Test Method for Hazeand Luminous Transmittance of Transparent Plastics. This test methodcovers the evaluation of specific light-transmitting andwide-angle-light-scattering properties of planar sections of materials,such as essentially transparent plastic. A procedure is provided for themeasurement of luminous transmittance and haze. Material having a hazevalue greater than 30% is considered diffusing. In this test method“haze” is defined as the cloudy or turbid aspect or appearance of anotherwise transparent specimen caused by light scattering from withinthe specimen or from its surfaces. It is measured as the percent oftotal transmitted light which, in passing through the specimen, deviatesfrom the incident beam through forward scatter by more than 0.044 rad(2.5°) on the average. Luminous transmittance is the ratio of theluminous flux transmitted by a body to the flux incident upon it.

The haze measurements were made by a hazemeter. The luminoustransmittance was obtained by placing a clear specimen at a distancefrom the entrance port of the integrating sphere.

The film of the present disclosure has a luminous transmittance greaterthan 30%, preferably greater than 50%, preferably greater than 75%,preferably greater than 85%.

The film of the present disclosure may exhibit a variable haze thatdepends on the individual application, for example from 10 to 90%.

The total thickness or gauge of the film is not limited; any filmthickness capable of being produced by co-extrusion techniques isapplicable. The total thickness of the film, for example, may be from 50to 1000 μm, preferably from 150 to 600 μm. The total width of the filmcan be from 1 to 25 meters, preferably 4 to 16 meters. Individual layersof the film are preferably from 0.03 to 300 μm each, more preferablyfrom 1 to 200 μm.

The (i) layer or layers comprising polyamide and/or ethylene vinylalcohol may have a thickness of from 0.03 to 300 μm, preferably from 1to 200 μm, more preferably from 2 to 100 μm.

To ensure that the film exhibits good solar properties, it will beappreciated by those skilled in the art that additives may be added toany of the layers to improve certain characteristics. This may depend onthe proposed use of the film and/or geographical locus. In certainembodiments, the additives may include UV stabilisers, antioxidants,anti-dripping agents, anti-fogging agents, anti-dust agents, IRabsorbers or reflectors, nucleating agents, nanocomposites,neutralisers, colour concentrates, slip agents, foaming agents,anti-statics, and speciality additives for specific applications.

In some embodiments, the UV stabilisers may include hindered amines,phosphites, benzophenones, benzotriazoles, salicylates, nickeldialkyldithiocarbamates and the like.

In some embodiments, the antioxidants include aromatic amines andsubstituted phenolic compounds. For example, phenyl-β-napthylamine,di-β-napthyl-p-phenylenediamine, butylated hydroxyanisole,di-tert-butyl-p-cresol and propyl gallate.

In some embodiments, the IR absorbers or reflectors include calcinedclay, silica and hydrotalcite.

In some embodiments, the neutralisers include calcium carbonate, calciumstearate and zinc stearate.

In some embodiments, the slip agents include silicones, stearamide,oleamide and erucamide. The slip agent may also be employed tofacilitate delamination of the polymer layers even further.

In some embodiments, the anti-dripping agents include sorbitan esters,ethoxylated sorbitan esters, glycerol esters and fatty acid esters.

In some embodiments, the anti-statics include substantiallystraight-chain and saturated aliphatic tertiary amines, ethoxylated orpropoxylated polydiorganosiloxanes, and alkali metal alkanesulfonates.

The polymeric film according to the present disclosure is produced usingknown co-extrusion techniques. The film can be the result of blownco-extrusion or cast co-extrusion. In some embodiments, the greenhousefilm described herein is produced using blown co-extrusion.

In the case of a co-extrusion blown film, a die is used to take two ormore melt streams entering the die and distribute them to a singleconcentric annular melt stream as uniformly as possible to the die exit,where the film is blown. Any type of die can be used for the presentdisclosure, including concentric mandrel dies, conical stacked mandreldies, modular plate designs and combined dies which combine features ofany of the aforementioned die arrangements.

According to the present disclosure, the film comprising at least twolayers and produced by co-extrusion technology, exhibits a layeredstructure in which at least two of the layers do not significantlyadhere to one another. Principally, this is achieved by the relativepolymeric compositions of the adjacent layers. However, it is alsopossible to further prevent adherence of adjacent layers by blowing airbetween them when the film is undergoing co-extrusion.

After the film has been blown it can be rolled and/or folded asappropriate. This means the resulting product can be easily transportedas a rolled laminate structure or as a folded film of desired size. Oncetransported to the site of erection, the film is unrolled and/orunfolded, brought into association with the relevant greenhouseframework and fixed in place. The layers are separated on one of thesides, a flange may be fixed to one or more of the separated layers,depending on the number of layers to be delaminated, and air is blownbetween to layers to inflate/delaminate the film. The air can beinserted between the layers by any means known in the art, and may beachieved using a centrifugal, radial or axial fan blower. The blower mayintroduce the air at a pressure of less than 20 kPa, preferably lessthan 15 kPa, more preferably less than 5 kPa, most preferably less than1.5 kPa. The pressure used may be greater than atmospheric pressure.

In use, the multilayered polymeric film according to the disclosurecontains (i) at least one layer comprising a polyimide and/or ethylenevinyl alcohol and (ii) at least one further polymer layer, wherein atleast 80% of layer (i) and layer (ii) are delaminated. In a preferableaspect at least 85% of layer (i) and layer (ii) are delaminated, morepreferably at least 90%, most preferably at least 95%.

The term “inflated” when used in relation to films is used to mean thatat least two layers of the film are separated over at least 50% of theirinterfaced area with a layer of air. “Inflated” covers films where twoor more of the layers are bonded around a portion or the whole of theirperiphery.

The film may or may not be sealed around the periphery of the film,although in some embodiments the film is substantially unsealed aroundthe periphery. In particular embodiments, the layers (i) and (ii) of thefilms of the present disclosure are bonded around less than 90% of theirperiphery, preferably less than 75%, preferably less than 50%,preferably less than 25%, preferably less than 10%. Bonding of thelayers (i) and (ii) around their peripheries may be 0% in certainembodiments of the disclosure. As used herein, “periphery” means theouter 1- to 20 cm edge of the film.

The film as described herein may exhibit various patterns ofdelamination. wherein certain areas of the film are provided withcharacteristics that do not allow the film to delaminate. This can beachieved by chemical means, such as by using adhesives or tie-materials,or by heat or plasma treatment of the film in specific areas. Further,this can also be achieved by mechanical blocking of e.g. layer i) atcertain points inside the die, thus allowing the other layers to bewelded at those points during production. The film can also be affixedto the greenhouse structure in such a way that only certain areas of thefilm can be delaminated. The film may exhibit regular or irregulartessellations of shapes with up to six sides, or may exhibit symmetricalor asymmetrical arrangements of channels and ridges.

The width of the film can vary in the range of from 1 to 25 meters,preferably from 4 to 16 meters, and the length can vary from 10 to 3000meters, preferably from 30 to 1000 meters. Nevertheless, it will beappreciated by those skilled in the art that the blown film may be cutinto any desired size or shape as required.

The film may be provided with specified fixation points, whichfacilitate attachment to the agricultural structure. These can bepredetermined points of the film. The fixation points, when present,include hooks for suspending the film from a structure and holes withreinforced rims (such as metal reinforced rings) through which bolts,rivets, clips or the like may pass.

The multilayered polymeric film or sheet of the present disclosure canbe used in association with an agricultural structure or greenhouse.More specifically, it can be used to cover at least a portion of theagricultural structure or greenhouse. Thus, in accordance with certainembodiments of the present disclosure, there is provided an agriculturalstructure or greenhouse, wherein the polymeric film (in either laminatedor delaminated form) described herein is attached thereto.

In certain embodiments of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer connected thereto, wherein layer (i) and layer (ii) arecapable of delamination from one another, the at least one furtherpolymer layer (ii) comprises a polymeric material selected from thegroup consisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, and the film hasa luminous transmittance greater than 30%, and layer (i) and layer (ii)have an average delamination strength of less than 100 g/15 mm,preferably less than 75 g/15 mm, even more preferably less than 30 g/15mm.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer connected thereto, wherein layer (i) and layer (ii) arecapable of delamination from one another, the at least one furtherpolymer layer (ii) comprises a polymeric material selected from thegroup consisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, and the film hasa luminous transmittance greater than 30%, the polymer of layer (i) isselected from the group consisting of polyamide 6, polyamide 6/6,polyamide 6/66, polyamide 6/610, polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide 6/12,polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylene vinylalcohol and combinations of two or more thereof, and layer (i) and layer(ii) have an average delamination strength of less than 100 g/15 mm,preferably less than 75 g/15 mm, even more preferably less than 30 g/15mm.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol and (ii) at least one furtherpolymer layer connected thereto, wherein the polymer of layer (i) isselected from the group consisting of polyamide 6, polyamide 6/6,polyamide 6/66, polyamide 6/610. polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide 6/12,polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylene vinylalcohol and combinations of two or more thereof, layer (ii) comprises apolymeric material selected from the group consisting of polyethylene,polypropylene, ethylene vinyl acetate copolymer, ethylene butyl acrylatecopolymer, thermoplastic polyurethane, other materials suitable forgreenhouse applications and combinations of two or more thereof, thefilm has a luminous transmittance greater than 30%, and layer (i) andlayer (ii) have an average delamination strength of less than 100 g/15mm, preferably less than 75 g/15 mm, even more preferably less than 30g/15 mm.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol and (ii) at least one furtherpolymer layer connected thereto, wherein the polymer of layer (i) isselected from the group consisting of polyamide 6, polyamide 6/6,polyamide 6/66, polyamide 6/610, polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide 6/12,polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylene vinylalcohol and combinations of two or more thereof, layer (ii) comprises apolymeric material selected from the group consisting of polyethylene,polypropylene, ethylene vinyl acetate copolymer, ethylene butyl acrylatecopolymer, thermoplastic polyurethane, other materials suitable forgreenhouse applications and combinations of two or more thereof, thefilm has a luminous transmittance greater than 30%, layer (i) and layer(ii) have an average delamination strength of less than 100 g/15 mm,preferably less than 75 g/15 mm, even more preferably less than 30 g/15mm and the total thickness of the film is from 50 to 1000 μm, preferablyfrom 150 to 600 μm and that the total width of the film is from 1 to 30metres.

In yet another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol and (ii) at least one furtherpolymer layer connected thereto, wherein the polymer of layer (i) isselected from the group consisting of polyamide 6, polyamide 6/6,polyamide 6/66, polyamide 6/610, polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide 6/12,polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylene vinylalcohol and combinations of two or more thereof, layer (ii) comprises apolymeric material selected from the group consisting of polyethylene,polypropylene, ethylene vinyl acetate copolymer, ethylene butyl acrylatecopolymer, thermoplastic polyurethane, other materials suitable forgreenhouse applications and combinations of two or more thereof, thefilm has a luminous transmittance greater than 30%, the film furthercomprises chemical or mineral additives selected from the groupconsisting of UV stabilisers, antioxidants, anti-dripping agents,anti-fogging agents, anti-dust agents, IR absorbers, nucleating agents,slip agents, nanocomposites and combinations of two or more thereof, andlayer (i) and layer (ii) have an average delamination strength of lessthan 100 g/15 mm, preferably less than 75 g/15 mm, even more preferablyless than 30 g/15 mm.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film or sheet comprises at least one layercomprising polyethylene from 100 to 200 μm thick, at least one layer ofa polyamide and/or ethylene vinyl alcohol from 5 to 50 μm thick and atleast one layer of ethylene butyl acrylate copolymer from 100 to 150 μmthick, wherein the polymer of layer (i) is selected from the groupconsisting of polyamide 6, polyamide 6/6, polyamide 6/66, polyamide6/610, polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T,polyamide 4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide6/69, polyamide 66/610 polyamide 6/12, polyamide 5/10, polyamide 6I,polyamide nanocomposites, ethylene vinyl alcohol and combinations of twoor more thereof, and at least one of the layers connected to thepolyamide and/or ethylene vinyl alcohol layer is capable of beingdelaminated, having an average delamination strength of less than 100g/15 mm, preferably less than 75 g/15 mm, even more preferably less than30 g/15 mm, and the film has a luminous transmittance greater than 30%.In this embodiment the film is capable of having one or more layers ofair separating the polymer layers.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film or sheet comprises at least one layercomprising polyethylene from 100 to 200 μm thick, at least one layer ofa polyamide and/or ethylene vinyl alcohol from 5 to 200 μm thick and atleast one layer of ethylene butyl acrylate copolymer from 100 to 200 μmthick, wherein the polymer of layer (i) is selected from the groupconsisting of polyamide 6, polyamide 6/6, polyamide 6/66, polyamide6/610, polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T,polyamide 4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide6/69, polyamide 66/610 polyamide 6/12, polyamide 5/10, polyamide 6I,polyamide nanocomposites, ethylene vinyl alcohol and combinations of twoor more thereof, and at least two of the layers connected to thepolyamide and/or ethylene vinyl alcohol layer are capable of beingdelaminated, each having an average delamination strength of less than100 g/15 mm, preferably less than 75 g/15 mm, even more preferably lessthan 30 g/15 mm, and the film has a luminous transmittance greater than30%. In this embodiment the film is capable of having two or more layersof air separating the polymer layers.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer, wherein at least 80% of the initial (laminated) interfaceof layer (i) and layer (ii) are delaminated, preferably at least 90%,even more preferably at least 95%, the at least one further polymerlayer (ii) comprises a polymeric material selected from the groupconsisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, and the film hasa luminous transmittance greater than 30%.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer, wherein at least 80% of the initial (laminated) interfaceof layer (i) and layer (ii) are delaminated, preferably at least 90%.even more preferably at least 95%, the at least one further polymerlayer (ii) comprises a polymeric material selected from the groupconsisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, the film has aluminous transmittance greater than 30%, and layer (i) and layer (ii)have an average delamination strength of less than 100 g/15 mm,preferably less than 75 g/15 mm, even more preferably less than 30 g/15mm.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer, wherein at least 80% of the initial (laminated) interfaceof layer (i) and layer (ii) are delaminated, preferably at least 90%,even more preferably at least 95%, the at least one further polymerlayer (ii) comprises a polymeric material selected from the groupconsisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, and combinations of two or more thereof, the film has aluminous transmittance greater than 30%, and the polymer of layer (i) isselected from the group consisting of polyamide 6, polyamide 6/6,polyamide 6/66, polyamide 6/610, polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide 6/12,polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylene vinylalcohol and combinations of two or more thereof.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol and (ii) at least one furtherpolymer layer, wherein at least 90% of the initial (laminated) interfaceof layer (i) and layer (ii) are delaminated, preferably at least 95%,the polymer of layer (i) is selected from the group consisting ofpolyamide 6, polyamide 6/6, polyamide 6/66, polyamide 6/610, polyamide6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T, polyamide 4/6,polyamide 11, polyamide 12, polyamide 6/10, polyamide 6/69, polyamide66/610 polyamide 6/12, polyamide 5/10, polyamide 6I, polyamidenanocomposites, ethylene vinyl alcohol and combinations of two or morethereof, layer (ii) comprises a polymeric material selected from thegroup consisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, other materials suitable for greenhouse applications andcombinations of two or more thereof, and the film has a luminoustransmittance greater than 30%.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film contains (i) at least one layer comprisinga polyamide and/or ethylene vinyl alcohol and (ii) at least one furtherpolymer layer, wherein at least 90% of the initial (laminated) interfaceof layer (i) and layer (ii) are delaminated, preferably at least 95%,the polymer of layer (i) is selected from the group consisting ofpolyamide 6, polyamide 6/6, polyamide 6/66, polyamide 6/610, polyamide6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T, polyamide 4/6,polyamide 11, polyamide 12, polyamide 6/10, polyamide 6/69, polyamide66/610 polyamide 6/12, polyamide 5/10, polyamide 6I, polyamidenanocomposites, ethylene vinyl alcohol and combinations of two or morethereof, layer (ii) comprises a polymeric material selected from thegroup consisting of polyethylene, polypropylene, ethylene vinyl acetatecopolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane, other materials suitable for greenhouse applications andcombinations of two or more thereof, the film has a luminoustransmittance greater than 30%. and the film further comprises chemicalor mineral additives selected from the group consisting of UVstabilisers, antioxidants, anti-dripping agents, anti-fogging agents,anti-dust agents, IR absorbers, nucleating agents, anti-slip agents,nanocomposites and combinations of two or more thereof.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film or sheet comprises at least one layercomprising polyethylene from 100 to 200 μm thick, at least one layer ofa polyamide and/or ethylene vinyl alcohol from 5 to 50 μm thick and atleast one layer of ethylene butyl acrylate copolymer from 100 to 150 μmthick, wherein the polymer of layer (i) is selected from the groupconsisting of polyamide 6, polyamide 6/6, polyamide 6/66, polyamide6/610, polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T,polyamide 4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide6/69, polyamide 66/610 polyamide 6/12, polyamide 5/10, polyamide 6I,polyamide nanocomposites, ethylene vinyl alcohol and combinations of twoor more thereof, the polyamide and/or ethylene vinyl alcohol layer andat least one of the layers connected thereto is at least 90%delaminated, preferably at least 95%, and the film has a luminoustransmittance greater than 30%. in this embodiment the film is capableof having one or more layers of air separating the polymer layers.

In another embodiment of the disclosure, there is provided amultilayered polymeric film for covering an agricultural structure orgreenhouse, wherein the film or sheet comprises at least one layercomprising polyethylene from 100 to 200 μm thick, at least one layer ofa polyamide and/or ethylene vinyl alcohol from 5 to 200 μm thick and atleast one layer of ethylene butyl acrylate copolymer from 100 to 200 μmthick, wherein the polymer of layer (i) is selected from the groupconsisting of polyamide 6, polyamide 6/6, polyamide 6/66, polyamide6/610, polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide 9T,polyamide 4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide6/69, polyamide 66/610 polyamide 6/12, polyamide 5/10, polyamide 6I,polyamide nanocomposites, ethylene vinyl alcohol and combinations of twoor more thereof, the polyamide and/or ethylene vinyl alcohol layer andat least two of the layers connected thereto are at least 90%delaminated, preferably at least 95%, and the film has a luminoustransmittance greater than 30%. In this embodiment the film is capableof having two or more layers of air separating the polymer layers.

In certain methods of the disclosure, there is provided a method ofcovering an agricultural structure or greenhouse with the polymeric filmcomprising the step of inserting air between the (i) at least one layercomprising the polyamide and/or ethylene vinyl alcohol and the (ii) atleast one further polymer layer, wherein the film contains (i) at leastone layer comprising a polyamide and/or ethylene vinyl alcohol and (ii)at least one further polymer layer connected thereto and wherein thepolymer of layer (i) is selected from the group consisting of polyamide6, polyamide 6/6, polyamide 6/66, polyamide 6/610, polyamide 6/6T,polyamide 6/3T, polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11,polyamide 12, polyamide 6/10, polyamide 6/69, polyamide 66/610 polyamide6/12, polyamide 5/10, polyamide 6I, polyamide nanocomposites, ethylenevinyl alcohol and combinations of two or more thereof, layer (ii)comprises a polymeric material selected from the group consisting ofpolyethylene, polypropylene, ethylene vinyl acetate copolymer, ethylenebutyl acrylate copolymer, thermoplastic polyurethane, other materialssuitable for greenhouse applications and combinations of two or morethereof, layer (i) and layer (ii) have an average delamination strengthof less than 100 g/15 mm, preferably less than 75 g/15 mm, even morepreferably less than 30 g/15 mm, the film has a luminous transmittancegreater than 30%, and the total thickness of the film or sheet is from50 to 1000 μm, preferably from 150 to 600 μm and that the total width ofthe film is from 1 to 30 metres.

In a final aspect of the present disclosure, there is provided analternative use of the multilayered polymeric film as a container linerfor packaging applications. In this aspect, the film may be delaminatedand inflated with gas to provide a multilayered liner in which thelayered structure ensures the packaging is not penetrated and contentsspoiled. The insertion of gas between the layers further providescushioning for any stresses the package may undergo, for example intransit to the marketplace.

The disclosure of separate embodiments and features is not intended tobe limiting. Separately disclosed embodiments, aspects and features maybe read together in combination and recited features may beinterchangeable.

EXAMPLES

Examples of multilayered polymeric film structures that can be employedin accordance with the disclosure are shown below.

Example 1

In this example of a multilayered polymeric film structure, layer A iscapable of being delaminated from layer B by the insertion of air.

  A: Polyethylene (150-200 μm) B: Polyamide (150-200 μm)

Example 2

In these examples of multilayered polymeric film structures, layer C iscapable of being delaminated from layers A and B which remain bondedtogether.

2a)   A: Polyethylene + 10-20% tie-material (140-190 μm) B: Polyamide(5-10 μm) C: Ethylene butyl acrylate (150-200 μm) 2b) A: Polyethylene +10-20% tie-material (140-170 μm) B: Polyamide (5-30 μm) C: Ethylenebutyl acrylate (150-200 μm)

Example 3

In these examples of multilayered polymeric film structures, layers Dand E remain bonded together and are capable of being delaminated fromlayers A, B and C which remain bonded together.

3a)   A: Polyethylene (130-190 μm) B: Polyethylene + 10-20% tie-material(5-10 μm) C: Polyamide (5-10 μm) D: Ethylene butyl acrylate (50-100 μm)E: Polyethylene (100-150 μm) 3b) A: Polyethylene (130-190 μm) B:Polyethylene + 10-20% tie-material (5-10 μm) C: Ethylene vinyl alcohol(5-10 μm) D: Ethylene butyl acrylate (50-100 μm) E: Polyethylene(100-150 μm) 3c) A: Polyethylene (130-160 μm) B: Polyethylene + 10-20%tie-material (5-20 μm) C: Polyamide (5-30 μm) D: Ethylene butyl acrylate(50-100 μm) E: Polyethylene (100-150 μm)

Example 4

In this example of a multilayered polymeric film structure, layer A iscapable of being delaminated from layer B and layer B is capable ofbeing delaminated from layer C. This allows for multiple layers of airto be inserted between delaminated layers for even better thermalinsulation properties.

  A: Polyethylene (100-200 μm) B: Polyamide (20-200 μm) C: Ethylenebutyl acrylate (100-200 μm)

In the same way it is possible to create an inflated multilayeredpolymeric film with 4, 5 or even more layers having air between them.

The disclosed structures are indicative as to the kind of materials perlayer, the number and thickness of the layers and of the whole polymericfilm. Each of the layers can contain blends of different materials aswell as different chemical or mineral additives, such as UV stabilizers,antioxidants, anti-dripping agents, anti-fogging agents, anti-dustagents, IR absorbers or reflectors, nucleating agents, nanocomposites,neutralisers, colour concentrates, slip agents, anti-statics, andspeciality additives for specific applications.

The invention claimed is:
 1. A method of covering an agriculturalstructure or greenhouse with a multilayered polymeric film, wherein thefilm contains (i) at least one layer comprising a polymer selected froma polyamide and ethylene vinyl alcohol, and (ii) at least one furtherpolymer layer connected thereto, wherein the (i) at least one layer andthe (ii) at least one further polymer layer have an average delaminationstrength of less than 250 g/15 mm when measured using ASTM D-1876, the(ii) at least one further polymer layer comprises a polymeric materialselected from the group consisting of polyethylene, polypropylene,ethylene vinyl acetate copolymer, ethylene butyl acrylate copolymer,thermoplastic polyurethane, and combinations of two or more thereof, andthe film has a luminous transmittance greater than 30%, wherein themethod comprises the step of inserting gas between the (i) at least onelayer comprising the polymer selected from a polyamide and ethylenevinyl alcohol, and the (ii) at least one further polymer layer todelaminate the (i) at least one layer and the (ii) at least one furtherlayer and create a layer of the gas between said layers so that themultilayered polymeric film is inflated when in use, wherein themultilayered polymeric film is co-extruded.
 2. The method according toclaim 1, wherein at least 80% of the (i) at least one layer and the (ii)at least one further polymer layer are delaminated from one another. 3.The method according to claim 1, wherein the (i) at least one layer andthe (ii) at least one further polymer layer have an average delaminationstrength of less than 100 g/15 mm.
 4. The method according to claim 1,wherein the (i) at least one layer contains greater than 20 wt % of thepolymer selected from a polyamide and ethylene vinyl alcohol.
 5. Themethod according to claim 1, wherein the polymer of the (i) at least onelayer is selected from the group consisting of polyamide 6, polyamide6/6, polyamide 6/66, polyamide 6/610, polyamide 6/6T, polyamide 6/3T,polyamide 6T, polyamide 9T, polyamide 4/6, polyamide 11, polyamide 12,polyamide 6/10, polyamide 6/69, polyamide 66/610, polyamide 6/12,polyamide 5/10, polyamide 61, polyamide nanocomposites, and ethylenevinyl alcohol.
 6. The method according to claim 1, wherein the (ii) atleast one further polymer layer contains greater than 10 wt % of thepolymeric material.
 7. The method according to claim 1, wherein the (i)at least one layer has a thickness of from 0.03 to 300 μm, the film hasa total thickness of from 50 to 1000 μm, and a total width of from 1 to25 meters.
 8. The method according to claim 7, wherein the (i) at leastone layer further comprises polyvinyl alcohol.
 9. The method accordingto claim 1, wherein the film further comprises from 1 to 20 additionallayers.
 10. The method according to claim 1, wherein the film furthercomprises chemical or mineral additives selected from the groupconsisting of UV stabilisers, antioxidants, anti-dripping agents,anti-fogging agents, anti-dust agents, IR absorbers, nucleating agents,slip agents, foaming agents, nanocomposites and combinations of two ormore thereof.
 11. The method according to claim 1, wherein the film isobtainable by blown or cast co-extrusion.
 12. The method according toclaim 1, comprising covering at least a portion of the agriculturalstructure or greenhouse with the film.
 13. The method of covering anagricultural structure or greenhouse according to claim 1, wherein thegas is inserted between the (i) at least one layer and the (ii) at leastone further polymer layer at a pressure of less than 20 kPa.
 14. Themethod according to claim 13, wherein the gas is atmospheric air. 15.The method according to claim 13, wherein the pressure is less than 15kPa.
 16. A method of covering an agricultural structure or greenhousewith a multilayered polymeric film, wherein the film contains (i) atleast one layer comprising a polymer selected from a polyamide andethylene vinyl alcohol, and (ii) at least one further polymer layer,wherein at least 50% of the (i) at least one layer and the (ii) at leastone further polymer layer are able to be delaminated, the (ii) at leastone further polymer layer comprises a polymeric material selected fromthe group consisting of polyethylene, polypropylene, ethylene vinylacetate copolymer, ethylene butyl acrylate copolymer, thermoplasticpolyurethane and combinations of two or more thereof, and the film has aluminous transmittance greater than 30%, wherein the method comprisesthe step of inserting gas between the (i) at least one layer comprisingthe polymer selected from a polyamide and ethylene vinyl alcohol, andthe (ii) at least one further polymer layer to delaminate the (i) atleast one layer and the (ii) at least one further layer and create alayer of the gas between said layers so that the multilayered polymericfilm is inflated when in use, wherein the multilayered polymeric film isco-extruded.
 17. The method according to claim 16, wherein at least 80%of the (i) at least one layer and the (ii) at least one further polymerlayer are delaminated from one another.
 18. The method according toclaim 16, wherein the (i) at least one layer and the (ii) at least onefurther polymer layer have an average delamination strength of less than100 g/15 mm.
 19. The method according to claim 16, wherein the (i) atleast one layer contains greater than 20 wt % of the polymer selectedfrom a polyamide and ethylene vinyl alcohol.
 20. The method according toclaim 16, wherein the polymer of the (i) at least one layer is selectedfrom the group consisting of polyamide 6, polyamide 6/6, polyamide 6/66,polyamide 6/610, polyamide 6/6T, polyamide 6/3T, polyamide 6T, polyamide9T, polyamide 4/6, polyamide 11, polyamide 12, polyamide 6/10, polyamide6/69, polyamide 66/610, polyamide 6/12, polyamide 5/10, polyamide 61,polyamide nanocomposites, and ethylene vinyl alcohol.
 21. The methodaccording to claim 16, wherein the (ii) at least one further polymerlayer contains greater than 10 wt % of the polymeric material.
 22. Themethod according to claim 16, wherein the (i) at least one layer has athickness of from 0.03 to 300 μm, the film has a total thickness of from50 to 1000 μm and a total width of from 1 to 25 meters.
 23. The methodaccording to claim 22, wherein the (i) at least one layer furthercomprises polyvinyl alcohol.
 24. The method according to claim 16,wherein the film further comprises from 1 to 20 additional layers. 25.The method according to claim 16, wherein the film further compriseschemical or mineral additives selected from the group consisting of UVstabilisers, antioxidants, anti-dripping agents, anti-fogging agents,anti-dust agents, IR absorbers, nucleating agents, slip agents, foamingagents, nanocomposites and combinations of two or more thereof.
 26. Themethod according to claim 16, wherein the film is obtainable by blown orcast co-extrusion.
 27. The method according to claim 16, comprisingcovering at least a portion of the agricultural structure or greenhousewith the film.
 28. The method of covering an agricultural structure orgreenhouse according to claim 16, wherein the gas is inserted betweenthe (i) at least one layer and the (ii) at least one further polymerlayer at a pressure of less than 20 kPa.
 29. The method according toclaim 28, wherein the gas is atmospheric air.
 30. The method accordingto claim 28, wherein the pressure is less than 15 kPa.